CMake: remove GIT_BIN_PARAM

CMake: remove GIT_BIN_PARAM

Added in adb731c1cd69855b1655a0f23001655392a07340 but never worked,
and later corrected in e21da738262af2ba6cf72f46fdc045f0337ca27e.
Correction however gave cygwin user problems with the perl optional parameter
which droped qoutes around the path. But since the orginal commit never worked
as intended in the beginning, it's assume safe to remove.

Change-Id: I825a4e53b257d47601c330b210ac5ffb6870e0d9
Reviewed-on: https://code.wireshark.org/review/27758
Reviewed-by: Peter Wu <peter@lekensteyn.nl>
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Reviewed-by: Anders Broman <a.broman58@gmail.com>